Laguna Pipes

[Gouki]

Hello Z28 Brethren,

Does anybody have some Laguna Seca low db exhaust pipes that they'd like to sell, or perhaps an off the shelf solution they can recommend?

It seems that the Z28 will blow about 95db on track and I'm trying to get to 92db.

Thanks!

[0stones0]

Originally Posted by Gouki

Hello Z28 Brethren,

Does anybody have some Laguna Seca low db exhaust pipes that they'd like to sell, or perhaps an off the shelf solution they can recommend?

It seems that the Z28 will blow about 95db on track and I'm trying to get to 92db.

Thanks!

No answer for you but, a question…
So the race track says the stock decibel of your Z is too loud or you have non stock exhaust that is pushing the limit?

[Gouki]

Laguna Seca has loud and quiet days at 103-105db and 90-92db respectively. The quiet days are half the price due to increased supply. My Z28 is stock, and based on my forum research will probably trigger the sound station between T5-T6, many folk run 'Laguna Pipes', which turn the exhaust direction away from the sound station or let off / use a higher gear for that section of the track. For context, the first video is a Laguna Seca hot lap, the second is an external microphone at Sonoma.

https://youtu.be/Obyrjtfcn64?feature=shared

https://youtu.be/MHgwdw6jq9A?feature=shared

[markstoys]

FYI, our cars (when stock, anyway) must be UNDER 95 dB, because I ran a 95 dB event a few years ago and had no problems. I'm not sure how much under 95, so you may not be OK if the limit is 92.

[Gouki]

Thanks for the info mark, I might just risk it and use fourth gear at the sound station instead of 3rd.

[IdahoRob]

If you still have the stock exhaust, you can just wire the muffler actuators in the closed position.

[void_kp]

Originally Posted by IdahoRob

If you still have the stock exhaust, you can just wire the muffler actuators in the closed position.

i wonder if "racing" with a closed exhaust is actually going to create issues to the engine... you have way more backpressure than needed and I also expect temperatures to rise significantly due to exhaust gasses not flowing out freely...

[IdahoRob]

Originally Posted by void_kp

i wonder if "racing" with a closed exhaust is actually going to create issues to the engine... you have way more backpressure than needed and I also expect temperatures to rise significantly due to exhaust gasses not flowing out freely...

I ran like this in Portland for 2 days at the track, didn't see any coolant/oil temp problems. Now I don't have EGT probes, and i would think they'd be higher, but within tolerable levels when engine is stock. I think the CATS have more flow issues than the factory muffler in quiet mode. Again, no hard data to back this up, just my thoughts. Why add an aftermarket, quieter muffler when you have something already on the car that does the same thing. Just my $.02

[void_kp]

Originally Posted by IdahoRob

I ran like this in Portland for 2 days at the track, didn't see any coolant/oil temp problems. Now I don't have EGT probes, and i would think they'd be higher, but within tolerable levels when engine is stock. I think the CATS have more flow issues than the factory muffler in quiet mode. Again, no hard data to back this up, just my thoughts. Why add an aftermarket, quieter muffler when you have something already on the car that does the same thing. Just my $.02

oh, I 100% agree with you. I was just poking this collective mind to see if there's also a downside. I also kept the original exhaust and forcing valves closed could be a very good option.

do you have some instruction to share on how you achieve it? (private works too in case you don't want to post it)

[IdahoRob]

Originally Posted by void_kp

oh, I 100% agree with you. I was just poking this collective mind to see if there's also a downside. I also kept the original exhaust and forcing valves closed could be a very good option.

do you have some instruction to share on how you achieve it? (private works too in case you don't want to post it)

Super easy, I just pulled the vacuum lines off of the actuators(flaps are open to straight through) then manually closed the actuators and used a metal zip tie. You could use some stainless wire also. Now the exhaust runs through the mufflers, really quite quiet. My wife was watching the track day and asked why my car was so quiet.

[Gouki]

Hey Rob, sorry to be a pain.

Could you take some photos of the mod? This sounds like a good approach.

[IdahoRob]

Originally Posted by Gouki

Hey Rob, sorry to be a pain.

Could you take some photos of the mod? This sounds like a good approach.

No worries, I'll take a couple but will be after the holidays.

[void_kp]

hey IdahoRob, resuming this because I'm planning to go to Laguna in MAy 2025. can you show me where the vacuum lines for the actuators are and where you "ziptied" the valves?

thank you very much!

[Gouki]

I actually installed the Forza 3-Way controller in the end. It works well, and I'll report back after mid March whether I pass 92db.

One thing to note is the continuous battery drain if left in quiet mode, I'm going to install a switch to power the system off when not in use. This is because fuse box closest to the controller in the trunk has a continuous live, rather than on ignition.